1. Field of the Invention
The present invention relates to insoles for use in footwear. More specifically, the present invention relates to methods and apparatus for insoles of the type having a heel section elevated above and fused to an inner sole via a step-down region to provide energy savings and a torsional spring capability to counteract pronation.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art
In the field footwear manufacturing, comfort is a touchstone in design and construction of shoes. Inherent in this criteria are the requirements of adequate support and shock absorption. The standard of support and shock absorption is often measured by the insole of the shoe. In many cases, the insole of shoes are constructed of materials which provide limited support, shock absorption and stability to the foot. After wearing shoes constructed in this manner for several hours, the lower extremities become fatigued and prone to injury.
While walking or running, the body weight normally lands on the outer lateral side of the heel. As the foot continues to move forward, the body weight is redistributed to the inside of the heel and then forward to the ball of the foot. Common foot conditions that affects many people include pronation and supination. Pronation is generally defined as the turning of the foot inwardly placing pressure on the medial, inside portion of the foot. Supination is defined as the turning of the foot outwardly placing pressure on the medical outside portion of the foot. Placing the limb in either position substantially increases the probability of injury.
When the foot pronates or supinates during walking, the body weight lands severely to the inside or outside of the heel, respectively, placing a pressure imbalance on the heel of the shoe. Such a position tends to unbalance the movement and to place undue strain on the bones and tendons in the foot increasing the tendency to twist the ankle or sprain the foot. The body weight must then be redistributed about the heel and forward to the ball of the foot under these unbalanced conditions. Thus, it is difficult to walk or run and there is a constant threat of injury. Further, shoes become worn much faster because the shoe construction adjacent to the inside or outside heel is worn down by the constant pressure imbalance.
Much effort has been expended in the past to overcome the lack of support, shock absorption and stability in shoe construction. Various devices for improving shoe construction and for addressing the effects of pronation have been known for a number of years. By way of example, several forms of such devices can be found in U.S. Pat. Nos. 4,611,413, 4,654,984 & 4,688,338 to Brown, U.S. Pat. Nos. 3,393,460 & 3,394,473 to Romen, U.S. Pat. No. 3,550,597 to Coplans, U.S. Pat. No. 4,232,457 to Mosher, and U.S. Pat. No. 4,783,910 to Boys II et al. Many of the structures known in the past taught planar insoles.
The '984 patent to Brown, illustrates a rigid orthotic insert having a reinforcing structure for a heel comprising a plurality of layers, each layer having graphite fibers positioned parallel to one another and oriented along an axis skewed from the longitudinal axis of the insert. A unitary construction is disclosed. The '473 patent to Romen discloses a rigid insole for a ladies' shoe having a shape-retaining construction including an elastic counter. A strip of spring steel is included to strengthen the framework of the shoe.
The '597 patent to Coplans discloses a foot supporting and corrective device with front and rear main torsional sections inclined with respect to each other. The main torsional sections are connected by an intermediate longitudinal extending section of relative stiff spring properties. The main torsional sections are twisted around a longitudinal axis A for yieldably maintaining the main torsional sections in their angular positions. The device is designed to provide torsional action similar to the natural torsionlike action of the foot. The '457 patent to Mosher discloses an orthotic insert of a resilient molded flexible plastic support member having a spongy resilient heel post mounted on the lower surface of the heel region A. The insert is flexible enough to accommodate variations in individuals feet yet resists flex sufficiently to beneficially limit excessive foot pronation. The '910 patent to Boys II, et al. discloses a shoe with an anti-G-force heel capsule having a heel pad and a semi-rigid heel counter. The heel capsule interacts with an anti-torsion member and an energy efficient forefoot midsole section, thus providing a support and cushioning system that absorbs shock and prevents excessive pronation.
Hence, those concerned with the development and use of insoles in the footwear manufacturing industry have long recognized the need for an improved insole incorporating an elevated heel section which "steps-down" to an inner sole having a torsional spring capability to counteract pronation or supination in a foot and to provide support, shock absorption and stability in footwear utilizing said insole where the insole equally counteracts pronation or supination by forcing the shoe into the correct position, and utilizes bi-lateral construction to optimize shock absorption and subsequent energy release to assist in walking, employs graphite construction to ensure strength and flexibility and thermoplastic resins to ensure cushioned but wear resistant properties, and is suitable for use in numerous shoe constructions. Thus, there is a need in the art for an improvement in shock absorbing and anti-pronation/anti-supination insoles utilized in footwear construction. The present invention fulfills all of these needs.